Porous Electrode for Electrochemical Cells

ABSTRACT

A porous electrode and methods of making the same are described. The porous electrode is comprised of a porous conductive layer and an insulating layer, where the pores inside the conductive layer function as mini-containers for the active metals for rechargeable batteries, and the insulating layer covers the top surface of the conductive layer and blocks the sites where active metal dendrites would otherwise preferentially grow. An example of such electrodes is a porous copper foil with top surface coated with polyvinylene difluoride. Electrochemical cells containing the invented electrodes, such as rechargeable lithium battery, sodium battery and aluminum battery, have good cycle life and safety performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Application No.15/721,719, and claims a priority date of Sep. 30, 2016 for U.S.provisional Patent Application 62/402932 filed on Sep. 30, 2016.

TECHNICAL FIELD

The present application relates generally to the field ofelectrochemical cells where a metal anode is used or formed, such asrechargeable lithium metal batteries, rechargeable sodium batteries,lithium air batteries, zinc air batteries, and aluminum air batteries.More particularly, this application relates to a conductive porouselectrode that has insulating surfaces. The present application alsorelates to methods of forming such electrodes, electrochemical cellscomprising such electrodes, and methods of making such electrochemicalcells.

BACKGROUND

With the broader adoption of portable electronic devices and electrifiedvehicles, there have been considerable need and interest forelectrochemical energy storage devices that have higher energy densitythan state-of-the-art lithium ion batteries. Metal anodes, such aslithium, sodium, zinc, magnesium and aluminum, are particularlyattractive as the anode of electrochemical cells because of their highenergy density, compared for example to intercalation carbon anodes oreven silicon anodes, where the presence of large amount of additionalelements increases weight and volume of the anodes, and thereby reducesthe energy density of the cells. However, electrochemical cells withmetal anodes, such as rechargeable lithium metal batteries, have cyclelife and safety problems associated with dendrite formation during thecharging process.

Solid polymer electrolyte is one of the current approaches to thedendrite problem. For example, U.S. Pat. Nos. 5,460,905 and 5,462,566describe a film of an n-doped conjugated polymer interposed between thealkali metal anode and the electrolyte. However, solid polymerelectrolyte has low conductivity, which is typically in the range of10-⁶ to 10-⁴ Siem at room temperature. At the same time, the polymerneeds to have high enough modulus to be able to resist the dendrite. Sothere is a dilemma for balancing the high conductivity need and highmodulus need. Another approach is to use single ion conductive ceramic,as for example stated in U.S. Pat. Application Nos. US 20140272524 andUS 20150318552, where protective layers of an alkali-ion conductingglassy or amorphous material are described. There remains a need forimproved methods which will enable the application of such high energydensity electrochemical cells.

SUMMARY OF THE INVENTION

An exemplary electrode of the present invention for use in anelectrochemical cell comprises: (i) a porous conductive layer whereactive metal, such as lithium, sodium, aluminum or zinc, is present orcan be incorporated; and (ii) an insulating layer that is made ofmaterial that is both electronically and ionically non-conductive,wherein the insulating material partially covers the conductive surfaceof the above-mentioned porous conductive layer.

The porous conductive layer of an exemplary electrode of the presentinvention is made of interconnected conductive materials, for example,copper, nickel, lithium, sodium, potassium, cesium, beryllium,magnesium, calcium, titanium, vanadium, iron, carbon, or any combinationof conductive materials. Preferably, the conductive material is selectedfrom copper, nickel, iron, carbon or their composites.

The pores in an exemplary porous conductive layer of the presentinvention are in the form of anything, for example, random shaped space,rectangular prism, hexagonal prism, cylinder, sphere, pyramid orcombination of any form. Dimension of the pores close to the insulatinglayer is particularly important. The average dimension of the poresclose to the insulating surface side of the porous conductive electrodeis preferably no more than 100 µm (10-⁶ m); more preferably, the averagedimension of the pores close to the insulating surface side of theporous conductive layer is no more than 10 µm; still more preferably,the average dimension of the pores close to the insulating surface sideof the porous conductive layer is no more than 5 µm. On the other hand,the average dimension of the pores close to the insulating surface sideof the porous conductive layer is preferably no less than 1 nm (10-⁹ m);more preferably, the average dimension of the pores close to theinsulating surface side of the porous conductive layer is preferably noless than 10 nm. Still more preferably, the average dimension of thepores close to the insulating surface side of the porous conductivelayer is no less than 100 nm.

The pores in an exemplary porous conductive layer of the presentinvention may occupy a significant volume of the porous conductivelayer. Preferably, the pore volume is more than 50% of the total volumeof the porous conducive layer. More preferably, the pore volume is morethan 75% of the total volume of the porous conducive layer.

The pores in an exemplary porous conductive layer of the presentinvention may be empty, partially filled or filled, with activematerials, with liquid electrolyte, with gel electrolyte, with solidelectrolyte, with composite electrolyte, or combination of the abovematerials.

The insulating layer of an exemplary electrode of the present inventionis made of non-conductive materials that are both electronically andionically non-conductive, for example, polymers, oxides, sulfides,fluorides, chloride, nitrides, carbonates, nitrides, silicates, borates,aluminates, sulfates, phosphates, and any combination of theabove-mentioned materials. Materials with low conductivity, goodadhesion and compatibility with other components of the electrochemicalcell are preferred.

Another aspect of the present invention pertains to methods for formingthe porous electrodes according to embodiments of the present invention.The layers of an exemplary electrode of the present invention may beformed by any of the methods, such as, but not limited to physical vapordeposition methods, chemical vapor deposition methods, electrostaticspray deposition methods, mechanical forming methods includingextrusion, chemical or electrochemical stripping or plating methods, orprinting methods including 2D and 3D printing. Low cost methods aregenerally preferred.

In one embodiment of the present invention, the insulating materialcovers only the space at the top of the conductive layer, whereas theuncovered top surface area of the conductive material is no more than50% of the available top surface area of the conductive material.Preferably, the uncovered top surface area of the conductive material isno more than 10% of the available top surface area of the conductivematerials. More preferably, the uncovered top surface area of theconductive material is no more than 1% of the available top surface areaof the conductive material.

In another embodiment of the present invention, the space containing theinsulating material extends to the inside of the conductive layer,whereas thickness of the space containing insulating material coveredportion of the conductive layer is preferably less than 100% of thetotal conductive layer thickness. More preferably, thickness of theinsulating material covered portion of the conductive layer is no morethan 50% of the total conductive layer thickness.

In one or more embodiments of the present invention, the electrode isincorporated as an anode or part of an anode into an electrochemicalcell that includes an anode, a cathode, and an electrolyte.

In one embodiment of the present invention, lithium metal is attached tothe porous electrode before being assembled into an electrochemicalcell.

In one or more embodiments of the present invention, lithium or sodiummetal is deposited in-situ to the porous electrode after the electrodeis assembled into an electrochemical cell.

The foregoing examples of related art with limitations related theretoare intended to be illustrative and not exclusive. The plural orsingular nouns used may indicate a class of substance or materialswithout distinction. Other limitations and teachings of the related artwill become apparent to those of skill in the art upon a reading of thespecification and a study of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates cross-sectional (left) and top (right) views of apart of the porous electrode of an embodiment of the present invention,where the insulation layer is on top of the conductive layer with randompores. 1: an uncovered top conductive material surface; 2: insulatinglayer; 3: a pore close to the insulating surface side of the porousconductive layer; 4: inner conductive material.

FIG. 2 illustrates cross-sectional (left) and top (right) views of apart of the porous electrode of an embodiment of the present invention,where the insulation layer extends deeper into the conductive layer withrandom pores. 1: an insulation material covered on top of the conductivematerial surface; 2: an uncovered top conductive material surface; 3: apore close to the insulating surface side of the porous conductivelayer; 4: inner conductive material without insulation coverage; LineAB: thickness of the space containing the insulation material; Line AC:thickness of the total conductive layer.

FIG. 3 illustrates cross-sectional (left) and top (right) views of apart of the porous electrode of an embodiment of the present invention,where the insulation layer is on top of the conductive layer withpatterned pores. 1: an uncovered top conductive material surface; 2:insulating layer; 3: a pore close to the insulating surface side of theporous conductive layer; 4: inner conductive material.

FIG. 4 illustrates a cross-sectional view of a porous electrode of anembodiment of the present invention, where active metal is sandwichedbetween additional current collector and an above-mentioned structure.1: insulating layer (uncovered top conductive surface may or may notexist); 2: porous conductive layer; 3: active metal layer (lithium,zinc, aluminum, sodium, etc.); 4: additional current collector.

FIG. 5 illustrates a cross-sectional view of a porous electrode of anembodiment of the present invention, where active metal is embeddedinside the pores of an above-mentioned structure without additionalcurrent collector. 1: insulating layer (uncovered top conductive surfacemay or may not exist); 2: porous conductive layer; 3: Active metal(lithium, zinc, aluminum, sodium, etc.) impregnated inside the pores ofthe porous conductive layer. No additional current collector is needed.

FIG. 6 illustrates a cross-sectional view of a porous electrode of anembodiment of the present invention, where an above-mentioned structureand additional current collector are combined. 1: insulating layer(uncovered top conductive surface may or may not exist); 2: porousconductive layer; 3: active metal (lithium, zinc, aluminum, sodium,etc.) impregnated inside the pores of the porous conductive layer; 4:additional current collector.

FIG. 7 illustrates a cross-sectional view of a porous electrode of anembodiment of the present invention, 1: insulating layer (uncovered topconductive surface may or may not exist); 2: porous conductive layer;Active metal (lithium, zinc, aluminum, sodium, etc.) would be depositedin-situ after assembling of the electrochemical cell. 3: additionalcurrent collector.

FIG. 8 illustrates a cross-sectional view of the active materialassembly of an electrochemical cell of an embodiment of the presentinvention. 1: insulating layer (uncovered top conductive surface may ormay not exist); 2: porous conductive layer; active metal (lithium, zinc,aluminum, sodium, etc.) would be deposited in-situ after assembling ofthe electrochemical cell. 4: additional current collector. 5: separatorlayer. 6: cathode layer.

FIG. 9 illustrate a cross-sectional view of the active material assemblyof an electrochemical cell of an embodiment of the present invention. 1:insulating layer, also functions as the separator layer (uncovered topconductive surface may or may not exist); 2: porous conductive layer;active metal (lithium, zinc, aluminum, sodium, etc.) would be depositedin-situ after assembling of the electrochemical cell. The pores may bepartially or completely filled with gel electrolyte or solidelectrolyte. 6: cathode layer.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The performance and safety problems caused by dendrite growth of theactive metal of a electrochemical cell where a metal anode is used orformed, such as rechargeable lithium metal batteries, rechargeablesodium batteries, lithium air batteries, zinc air batteries, andaluminum air batteries, may, according to the present invention, besolved by the use of a porous conductive electrode comprising aninsulating surface layer.

Porous Electrodes

One aspect of the present invention pertains to a porous electrode foruse in an electrochemical cell, wherein the porous electrode comprises:

-   (i) a porous conductive layer where active materials, such as    lithium, magnesium, sodium, aluminum or zinc, is present or can be    incorporated; and-   (ii) an insulating layer made of material that is both    electronically and ionically non-conductive, wherein the insulating    material partially covers the conductive surface of the above porous    conductive layer.

The porous electrode of embodiments of the present invention may furthercomprise other components, for example, additional current collector,gel electrolyte, solid electrolyte, and/or active metal.

Porous Conductive Layer

The porous conductive layer of the electrode of embodiments of thepresent invention functions as: (i) the current collector, whereelectric current can flow in and out from; (ii) the substrate, where theactive metal can be deposited to or stripped from; and (iii) thecontainer, where the active metal can be contained inside and dendritegrowth can be blocked.

The porous conductive layer of the electrode of embodiments of thepresent invention is made of interconnected conductive material. Aconductive material is defined here as any substance that has anelectronic conductivity of no less than 10-⁶ Siem at ambient conditions,for example, copper, nickel, sodium, potassium, cesium, beryllium,magnesium, calcium, titanium, vanadium, iron, carbon, conductivepolymers, such as doped polythiophenes, conductive ceramics, such asdoped indium tin oxide, or any combination of conductive substance. Theconductive material may be in any form of shape, such as wire, ribbon,tube, mesh or foam, and be arranged in a regular pattern, in mixedpatterns, or in a random fashion. Preferably, the conductive material isselected from copper, nickel, iron, carbon or their composites, and thepreferable patterns will be those economical to make, such as random,circular, triangular, and rectangular.

The pores in the porous conductive layer of embodiments of the presentinvention may occupy a significant volume of the porous conductivelayer. Preferably, the pore volume is no less than 50% of the totalvolume of the porous conducive layer. More preferably, the pore volumeis no less than 75% of the total volume of the porous conducive layer.

The thickness of the porous conductive layer is not particularlylimited. For practical reasons, the thickness is not to be over 10 cm.For portable electronic applications, the thickness is preferably not tobe over 1 cm. For various applications, the thickness can be, forexample, 10 cm, 1 cm, 1 mm, 100 µm, 10 µm, 1 µm, 0.1 µm or any number inbetween.

Insulating Layer

The insulating layer of the electrode of embodiments of the presentinvention is made of material that is both electronically and ionicallynon-conductive. “Non-conductive” means very low conductivity, forexample, less than 10-⁶ Siem at ambient conditions. The insulatingmaterial partially covers the surface of the conductive material of theabove porous conductive layer and inhibits preferential deposition andgrowth of the active metal on the outside surface of the conductivelayer while leaving the pores open for the flow of electrolyte and/orions.

The insulating material that is contained in the insulating layer of theelectrode of embodiments of the present invention can be anynon-conductive materials, such as polymers, oxides, sulfides, fluorides,chlorides, carbonates, nitrides, silicates, borates, aluminates,sulfates, phosphates and mixed compounds. Mixed compounds are the oneswith more than one cation or more than one negatively charged element inits structure, such as LiAlMgF4 and LixPOyNz, LixPOyFz, where x,y,z = ⅓,½, 1, 1.5, 2 or 3, provided the charge is balanced for the formula.Specific examples of the non-conductive material include polyethylene(PE), polypropylene (PP), polystyrene (PS), polytetrafluoroethylene(PTFE), polyvinyldifluoride (PVDF), polyacrylic acid (including itsesters) (PAA), polyamide (PA), poly(terephthalate) (PT), LiF, LizO,LizS, LizCO3, LhPO4, LiPO2F2, AhO3, AlF3,AlPO4, ZnF2, Zn3(PO4)z and anycombination of the above-mentioned compounds. Material with lowerconductivity, good adhesion and compatibility with other components ofthe electrochemical cell is preferred.

The thickness of the space containing the insulating material depends onthe porous conductive layer. Generally speaking, the thickness of thespace containing the insulating material is less than the thickness ofthe conductive layer. For practical reasons, the thickness of the spacecontaining the insulating material is not to be over 1 cm. For portableelectronic applications, the thickness is preferably not to be over 1mm. For various applications, the thickness can be, for example, 1 cm, 1mm, 0.1 mm, 10 µm, 1 µm, 0.1 µm, 10 nm.

Poresoftheporouselectrode

The pores in the porous conductive layer of embodiments of the presentinvention are the space where an active material can be stored. Thepores can be in the form of anything, for example, random-shaped space,rectangular prism, hexagonal prism, cylinder, sphere, pyramid or acombination of any form. The dimensions of the pores close to theinsulating layer and the interface is of particular importance. Theaverage dimension of a pore close to the insulating surface side of theporous conductive layer is preferably no more than 100 µm; morepreferably, the average dimension of the pores close to the insulatingsurface side of the porous conductive layer is no more than 10 µm; stillmore preferably, the average dimension of the pores close to theinsulating surface side of the porous conductive layer is no more than 5µm. On the other hand, the average dimension of the pores close to theinsulating surface side of the porous conductive layer is preferably noless than 1 nm; more preferably, the average dimension of the poresclose to the insulating surface side of the porous conductive layer ispreferably no less than 5 nm. Still more preferably, the averagedimension of the pores close to the insulating surface side of theporous conductive layer is no less than 10 nm.

The pores in the porous conductive layer of embodiments of the presentinvention occupy a significant volume of the porous conductive layer, somore active materials can be stored in a given electrode volume.Preferably, the pore volume is no less than 50% of the total volume ofthe porous conducive layer. More preferably, the pore volume is no lessthan 75% of the total volume of the porous conducive layer.

The pores in the porous conductive layer of embodiments of the presentinvention may be empty, partially filled or filled, with activematerials, with liquid electrolytes, with gel electrolyte, with solidelectrolyte, with composite electrolyte, or any combination of theabove.

Uncovered Top Conductive Surface of the Porous Conductive Layer

The top conductive surface of the porous conductive layer broadly refersto the surface of the conductive material that is close to or in contactwith the insulating layer and faces toward the direction of theinsulating layer. The exact thickness of the conductive layer that isconsidered part of the top conductive surface may depend on the diameterof the pores of the conductive layer that borders the insulating layer.Generally, the bigger the pore diameter, the thicker the portion of theconductive layer would be considered containing the top conductivesurface. For example, for a pore diameter of 2 µm, the surface of theconductive material that locates within 1.5 µm of the porous conductivelayer bordering the insulating layer may be considered the topconductive surface; for a pore diameter of 5 µm, the surface of theconductive material that locates within 2.5 µm of the porous conductivelayer bordering the insulating layer may be considered the topconductive surface. Any uncovered top conductive surface would providepreferential sites for dendrite growth. Ideally, the insulating materialshould cover the entire top conductive surface of the porous conductivelayer. Practically, there may be some uncovered top conductive surfaceleft.

The insulating material may cover only the very top of the conductivelayer, whereas the uncovered top surface area of the conductive elementis no more than 50% of the available top surface area of the conductiveelements. Preferably, the uncovered top surface area of the conductiveelement is less than 10% of the available top surface area of theconductive elements. More preferably, the uncovered top surface area ofthe conductive element is less than 1% of the available top surface areaof the conductive elements.

The insulating material coverage may extend farther to the inside of theconductive layer, wherein the thickness of the covered portion of theconductive layer is preferably less than 50% of the total conductivelayer thickness. More preferably, the thickness of the covered portionof the conductive layer is less than 25% of the total conductive layerthickness.

Optional Components of the Porous Electrode

Active metal, such as lithium, sodium, zinc, magnesium or aluminum, mayor may not be present in the porous electrode. When the active metal isnot present, the active metal may be deposited into the electrode afterassembly of the electrochemical cell. When the active metal is present,it may be either: stacked under the porous conductive layer, orimpregnated inside the pores of the porous conductive layer.

Additional current collectors may or may not be present. When it ispresent, it can be either in the form of solid sheet, mesh or foam.

Method of Forming the Porous Electrode and Use Thereafter

Another aspect of the present invention pertains to the method offorming the porous electrode. The layers of the electrode of embodimentsof the present invention may be formed by any of the methods, such as,but not limited to physical deposition methods, chemical vapordeposition methods, electrostatic spray deposition, mechanical formingmethods including extrusion, winding and molding, chemical orelectrochemical stripping or plating, or printing methods including 2Dand 3D printing. Low cost methods are generally preferred.

One more aspect of the present invention pertains to any use of theporous electrode. In one or more embodiments of the present invention,the porous electrode is incorporated as an anode or part of the anodeinto an electrochemical cell that includes an anode, a cathode, aseparator and an electrolyte. In an alternative embodiment of thepresent invention, the porous electrode is incorporated as an anode orpart of the anode into an electrochemical cell that includes an anode, acathode, and an electrolyte.

In an alternative embodiment of the present invention, lithium metal isattached to the porous electrode before being assembled into anelectrochemical cell.

In alternative embodiments of the present invention, lithium or sodiummetal is deposited in-situ to the porous electrode after the electrodeis assembled into an electrochemical cell.

The electrode of embodiments of the present invention when incorporatedinto an electrochemical cell enables the active metal to be storedinside the pores and inhibit the preferential growth of active metaldendrite during charging. The electrochemical cells containingembodiments of the present invention have high energy density, goodcycle life, experience little volume change during operation, and/orhave improved safety.

EXAMPLES

Several embodiments of the present invention are described in thefollowing examples, which are offered by way of illustration and not byway of limitation.

Example 1: In one embodiment, a thin copper foil is first press fixedonto a platinum foil face to face and then attached to the workingterminal of a potentiostat/galvanostat. The foils are then immersed intoa CuSO4/H2SO4 aqueous solution. After setting up the platinum counterelectrode and Ag/AgCl reference electrode, positive current pulse isapplied to the copper foil to randomly strip copper and thus a porouscopper foil is obtained. The perforated copper foil is then separatedfrom the platinum foil and one side protected with a Scotch tape andattached again to the working terminal of the potentiostat/galvanostat.Negative current pulse is then applied to the copper foil and randomcopper is grown onto the perforated copper foil. Thus a porousconductive layer made of copper is obtained. The porous copper foil isintroduced into a physical vapor deposition chamber as the substratetogether with a LiF target. After the desirable vacuum is obtained, LiFis deposited onto the copper mesh. A porous electrode as illustrated inFIG. 1 is thus prepared.

Example 2: In an alternative embodiment, a loose fine copper wire pilewith thickness of 10 cm is dipped into a melted PE pan of 1 cm deep.Then the copper wire was allowed to cool slowly so that PE uniformlycovers one tenth of the copper wire piles thickness. The copper wirepile was then pressed into a thickness of 1 cm. Thus a porous electrodeas illustrated in FIG. 2 is prepared.

Example 3: In an alternative embodiment, a nickel mesh with average toplayer pore size less than 10 µm is introduced into a physical vapordeposition chamber as the substrate together with a LiF target. Afterthe desirable vacuum is obtained, LiF is deposited onto the nickel mesh.Thus a porous electrode as illustrated in FIG. 3 is prepared.

Example 4: In an alternative embodiment, a brass alloy sheet of 50 µmisimmersed in a IM HCl solution until no gas bubble is generated. Thesheet is then connected to the ground terminal of an electrostatic spraydeposition chamber and is heated to 250° C. A 10 kV is applied on themetal needle connected to a vial of PVDF solution and the copper sheetis coated for 5 minutes. Thus a porous electrode as illustrated to FIG.1 is prepared.

Example 5: In an alternative embodiment, a porous electrode from example3 is stacked on top of a lithium foil and copper foil. Thus a porouselectrode as illustrated in FIG. 4 is prepared.

Example 6: In an alternative embodiment, a porous electrode from example3 is introduced into a vacuum chamber and placed upside down as thesubstrate. Lithium was then deposited onto the bottom surface and poresof the nickel mesh. Thus a porous electrode as illustrated in FIG. 5 isprepared.

Example 7: In an alternative embodiment, a porous electrode from example6 stacked onto a nickel foil. Thus a porous electrode as illustrated inFIG. 6 is prepared.

Example 8: In an alternative embodiment, a porous electrode from example3 is stacked on top of copper foil. Thus a porous electrode asillustrated in FIG. 7 is prepared.

Example 9: In an alternative embodiment, a porous electrode from example3 is stacked on top of an aluminum foil and nickel foil. Thus a porouselectrode as illustrated in FIG. 4 is prepared.

Example 10: In an alternative embodiment, a porous electrode fromexample 3 is stacked on top of a zinc foil and nickel foil. Thus aporous electrode as illustrated in FIG. 4 is prepared.

Example 11: In an alternative embodiment, a porous electrode fromexample 7 is cut into a rectangular shape with a tab, then stacked witha PP separator and an LiNio.6Coo.2Mno.2O2 based cathode sheet of thematching shape and size. Thus an active material assembly stack asillustrated in FIG. 8 is prepared. The stack is then partially sealedinside a pouch bag with attached tabs sticking out. IM LiPF6 in EC/EMC3/7 v is then added to the pouch bag and the pouch bag is finally vacuumsealed in a dry room. An electrochemical cell of an embodiment of thepresent invention is thus prepared.

Example 12: In an alternative embodiment, a porous electrode fromexample 3 is cut into a rectangular shape with a tab, then stacked withan LiFePO4 based cathode sheet of the matching shape and size. Thus anactive material assembly stack as illustrated in FIG. 9 is prepared. Thestack is then partially sealed inside a pouch bag with attached tabssticking out. 2M LiFSI in EC/PC 1/1v is then added to the pouch bag andthe pouch bag is finally vacuum sealed in a dry room. An electrochemicalcell of an embodiment of the present invention is thus prepared.

Example 13: In an alternative embodiment, a porous electrode fromexample 3 is cut into a circular shape with a tab, then stacked with anLiMn2O4 based cathode sheet of the matching shape and size. Thus anactive material assembly stack as illustrated in FIG. 9 is prepared. Thestack is then partially sealed inside a pouch bag with attached tabssticking out. 1.2M LiPF6 in EC/EMC 3/7 vis then added to the pouch bagand the pouch bag is finally vacuum sealed in a dry room. Anelectrochemical cell of an embodiment of the present invention is thusprepared.

Example 14: In an alternative embodiment, a porous electrode fromexample 3 is cut into a rectangular shape with a tab, then stacked withan LiCoO2 based cathode sheet of the matching shape and size. Thus anactive material assembly stack as illustrated in FIG. 9 is prepared. Thestack is then partially sealed inside a pouch bag with attached tabssticking out. 3M LiPF6 in EC/EMC 1/1 vis then added to the pouch bag andthe pouch bag is finally vacuum sealed in a dry room. An electrochemicalcell of an embodiment of the present invention is thus prepared.

Example 15: In an alternative embodiment, a porous electrode fromexample 3 is cut into a rectangular shape with a tab, then stacked witha Na2FePO4F based cathode sheet of the matching shape and size. Thus anactive material assembly stack as illustrated in FIG. 9 is prepared. Thestack is then partially sealed inside a pouch bag with attached tabssticking out. 2M NaPF6 in EC/EMC 1/1 vis then added to the pouch bag andthe pouch bag is finally vacuum sealed in a dry room. An electrochemicalcell of an embodiment of the present invention is thus prepared.

Example 16: In an alternative embodiment, a porous electrode fromexample 3 is cut into a rectangular shape with a tab, then stacked witha LiCoO2 based cathode sheet of the matching shape and size. Thus anactive material assembly stack as illustrated in FIG. 9 is prepared. Thestack is then partially sealed inside a pouch bag with attached tabssticking out. IM LiPF6 in EC/EMC 1/1 v solution with 6%wt (by weight) ofmethyl methacrylate (MMA) and 0.1%wt AIBN (initiator) is then added tothe pouch bag and the pouch bag is finally vacuum sealed in a dry room.The pouch bag is then stored at 60° C. for 12 hours and so that MMA ispolymerized and the electrolyte in the pores becomes solid. Anelectrochemical cell of an embodiment of the present invention is thusprepared.

The electrochemical cells that contain embodiments of the presentinvention have good cycle life, experience small volume change duringoperation, and/or have good safety performance.

I claim:
 1. (canceled)
 2. A composition, comprising: a conductivematerial having a volume and defining pores having an average dimensionof between 1 nm and 100 micrometers, wherein the pores have a volumethat is no less than 50% of the volume of the conductive material; andan electronically and ionically non-conductive material in contact withand partially covering a surface of the conductive material withoutcovering at least some of the pores of the conductive material.
 3. Thecomposition of claim 2, wherein the non-conductive material extends intoat least some of the pores of the conductive material.
 4. Thecomposition of claim 2, wherein the conductive material has aconductivity of no less than 10⁻⁶ S/cm.
 5. The composition of claim 2,wherein the surface of the conductive material is partially covered bythe non-conductive material and has a total conductive surface area, andwherein the conductive material has an uncovered conductive surface areathat is less than 10% of the total conductive surface area.
 6. Thecomposition of claim 5, wherein the uncovered surface area of theconductive material is less than 1% of the total surface area of theconductive material.
 7. The composition of claim 2, wherein theconductive material comprises carbon.
 8. The composition of claim 2,wherein the conductive material comprises one or more of copper ornickel.
 9. The composition of claim 2, wherein the pores have a volumethat is more than 75% of the volume of the conductive material.
 10. Thecomposition of claim 2, wherein the non-conductive material comprises apolymer.
 11. The composition of claim 2, wherein the non-conductivematerial comprises polyethylene (PE).
 12. The composition of claim 2,wherein the non-conductive material comprises one or more ofpolypropylene (PP), polystyrene (PS), polytetrafluoroethylene (PTFE),polyvinyldifluoride (PVDF), polyacrylic acid (including its esters)(PAA), polyamide (PA), polyester (PES), or poly(terephthalate) (PT). 13.The composition of claim 2, wherein the non-conductive materialcomprises a ceramic.
 14. The composition of claim 2, wherein thenon-conductive material comprises LiF.
 15. The composition of claim 2,wherein the non-conductive material comprises one or more of Li₂O, Li₂S,Li₂CO₃, Li₃PO₄, LiPO₂F₂, Al₂O₃, AlF₃, AlPO₄, ZnF₂, or Zn₃(PO₄)₂.
 16. Anelectrochemical cell, comprising: an electrode comprising thecomposition of claim 2; an opposite electrode; and an electrolytepositioned between the electrode and the opposite electrode.
 17. Theelectrochemical cell of claim 16, wherein at least some of the pores arepartially or completely filled with the electrolyte.
 18. Theelectrochemical cell of claim 16, wherein at least some of the porescontain an active metal.
 19. The electrochemical cell of claim 18,wherein the active metal comprises lithium.
 20. The electrochemical cellof claim 18, wherein the active metal comprises an active metal selectedfrom the group consisting of sodium, aluminum, magnesium and zinc.
 21. Acomposition, comprising: a conductive material having a volume anddefining pores having an average dimension of between 1 nm and 100micrometers; and an electronically and ionically non-conductive materialin contact with and partially covering a surface of the conductivematerial without covering at least some of the pores of the conductivematerial, wherein the non-conductive material extends into at least someof the pores of the conductive material.
 22. A composition, comprising:a conductive material having a volume and defining pores having anaverage dimension of between 1 nm and 100 micrometers; and anelectronically and ionically non-conductive material in contact with andpartially covering a surface of the conductive material without coveringat least some of the pores of the conductive material, wherein thesurface of the conductive material is partially covered by thenon-conductive material and has a total conductive surface area, andwherein the conductive material has an uncovered conductive surface areathat is less than 10% of the total conductive surface area.